Provided is a strain sensor that includes a fixing section and a measurement section that is supported by the fixing section and can expand and contract. The strain sensor includes a base material that has a first main surface and a second main surface, which face each other, and a conductor section provided on the first main surface. The conductor section includes a detection conductor that is provided in the measurement section and that has a resistance value that changes in accordance with expansion and contraction of the base material in the measurement section. The measurement section includes a detection section in which the detection conductor is provided and a low-elastic-modulus section that increases a deformation amount with respect to an external force in the detection section.